The adornment, repairing and prosthetic extension of keratinaceous structures such as human fingernails and toe nails have been common practice for many years. Currently, it is known for human fingernails to be repaired with cyanoacrylate adhesives and coated with multicolored nitrocellulose and the like lacquers as well as being extended with the use of polymerizable acrylic monomer and polymer slurries or doughs. Although the nitrocellulose lacquer coatings and cyanoacrylate adhesives are generally adherent to proteinaceous substrates such as a human fingernail plate, the acrylic materials employed for the purpose of creating an artificial fingernail prosthesis and the like are not. Over the years a variety of in-situ polymerizable acrylic monomer and polymer slurry and dough compositions have been suggested for use as artificial fingernail prosthesis such as disclosed, for example, in U.S. Pat. Nos. 3,928,113; 4,048,442; 4,104,333; 4,229,431; 4,626,428; 4,669,491; 4,766,005; 4,871,534; 5,098,696 and 5,523,076.
Typically, only after treatment of the fingernail surface with an unsaturated carboxylic acid, such as methacrylic acid, will such polymerizable or cured acrylic compositions used for fingernail prosthesis adhere to the human fingernail plate, and even then, adhesion of the polymerized artificial fingernail materials may not persist for extended periods during normal use or until it is desired to remove the artificial fingernail. Moreover, use of such unsaturated carboxylic acids present a harsh treatment to a relatively fragile surface such as a natural human fingernail plate and poses a toxicological and dermatological hazard to living tissue of the user such as the underlying or surrounding living tissue of the fingernail plate due to the corrosive nature of these unsaturated carboxylic acids. Needless to say, "child-proof" packaging may be required for such hazardous materials. Other unsaturated carboxylic acids are also being used in the described applications including, either alone or in part, acrylic acid and beta-carboxyethyl acrylate as well as other compounds containing acid moieties. Lower concentration of these unsaturated carboxylic acids pose a decreased danger to the intact fingernail surface. However, at such lower concentrations adhesion of the polymerizable acrylic monomer and polymer slurry or dough to the fingernail plate is reduced or lost completely.
Currently, the typical known and readily practiced method for obtaining adhesion of artificial prosthetic materials to proteinaceous substrates, such as human fingernails, has been the physical abrasion and/or roughening of the proteinaceous substrate surface with a file or other abrasive material, the application of unsaturated carboxylic acid solutions as primers followed by the application and curing of the prosthetic topcoat material. These methods and materials present certain disadvantages as indicated which may be harmful to the human fingernail itself as well as to the underlying or surrounding tissue while such harsh techniques effect adhesive bonds which are frequently inadequate.
It follows from the above mentioned disadvantages that there is a need for materials and methods which are safe to use for the application of protective coatings and adhesives to proteinaceous substrates and the like and will provide improved adhesion of the coatings and adhesives such as artificial fingernail materials to proteinaceous substrates such as human fingernails. Particularly advantageous are materials and methods which effect adhesion of coating materials to the proteinaceous substrates for extended periods, preferably until it is desired by the user to remove the artificial fingernail coating, and the materials and methods reduce the preparation time and complexity of the procedure needed.